Air ionizers which emit a flow of positively and negatively charged ions have to date, proven most effective in neutralizing accumulated static charge on a non-conductive object within the ionized airstream. Typically, airstream ionizers place a high voltage potential on one or more emitter points to initiate the ionization process or corona, in the hopes of emitting an airstream containing an equal number of positive and negative ions. Measurements have shown, however, that various factors influence the generation of a balanced ion stream and cause the ionizer to output an airstream which is itself charged. For example, the greater mobility of negative ions, and ground planes formed by the metal case of the ionizer in close proximity to the emitters, cause an imbalance in the positive and negative ions emitted by the ionizer. This charge imbalance is subsequently transferred to any object in the path of the airstream, thereby adding to the problem that the air ionizer was designed to eliminate. In addition, dirt on the emitter points as well as humidity in the air affect the ionization process.
Various mechanical techniques are known to balance the production of positive and negative ions delivered by the ionizer at a given moment under given conditions. Such techniques include adjusting the position of the emitters relative to the collector or using external sensors and feedback mechanisms. However, continuously changing environmental conditions as well as the constant accumulation of dirt on the emitters make these approaches ineffective.
Attempts have been made to achieve a passively balanced ionized air stream by causing the ion emitters to give off positive and negative ions equally. In such a system, the one or more emitter points are capacitively isolated from the high side of an AC power source. Although negative ions are generally easier to produce and can be produced at lower voltages because of the physics involved in air ionization, a system utilizing capacitively coupled emitters overcomes this excess negative ion production. In such a system, the emitter points become slightly positively charged. This positive charge adds algebraically to the positive charge present during the positive going portion of the AC waveform, thus producing more positive ions. The increased production of positive ions continues until an equal number of positive and negative ions are generated.
Even though the emitter circuit is now generating a balanced amount of positive and negative ions, it has been found that the charge of the ionized airstream exiting the ionizer is not balanced.